Joseph Keith

A cyber security researcher "accidentally" stumbled upon a 'kill switch', reportedly slowing the spread of the online virus that has swept across the world.

The WannaCry ransomware, a virus that attacks IT systems, caused chaos for the NHS, including hospital trusts in Yorkshire, when the cyber attacks first began at around 3.30pm yesterday (Friday).

It later spread to more than 70 other countries and has now affected a range of organisations.

However, a cyber security researcher reportedly managed to slow the spread of the online virus after locating and activating a 'kill switch'.

The researcher, using the pseudonym @malwaretechblog, said in a new blog post that he found the 'kill switch' by registering a cheap domain name that was hidden inside the malicious software.

In the blog post, he describes at detail how he analysed, tracked and eventually slowed down the ransomware.

He said: "Now you probably can’t picture a grown man jumping around with the excitement of having just been ransomwared, but this was me.

"The failure of the ransomware to run the first time and then the subsequent success on the second mean that we had in fact prevented the spread of the ransomware and prevented it ransoming any new computer since the registration of the domain."

By activating the 'kill switch', experts say it bought time for some countries to create firewalls blocking the attack.

@malwaretechblog has also created a live tracking map showing where the ransomware was striking across the world.

At least 30 health service organisations in England and Scotland were infiltrated by the malicious software, while many others shut down servers as a precautionary measure, bringing added disruption.

In Yorkshire, York Teaching Hospital NHS Trust and Hull and East Yorkshire Hospitals NHS Trust both confirmed they were being affected by the malware yesterday.